Methane and Nitrogen Oxide Fluxes in Tropical Agricultural Soils: Sources, Sinks and Mechanisms

Tropical soils are important sources and sinks of atmospheric methane (CH₄) and major sources of oxides of nitrogen gases, nitrous oxide (NM_2O) and NO_x (NO+NO₂). These gases are present in the atmosphere in trace amounts and are important to atmospheric chemistry and earth's radiative balance. Although nitric oxide (NO) does not directly contribute to the greenhouse effect by absorbing infrared radiation, it contributes to climate forcing through its role in photochemistry of hydroxyl radicals and ozone (O₃) and plays a key role in air quality issues. Agricultural soils are a primary source of anthropogenic trace gas emissions, and the tropics and subtropics contribute greatly, particularly since 51% of world soils are in these climate zones. The soil microbial processes responsible for the production and consumption of CH₄ and production of N-oxides are the same in all parts of the globe, regardless of climate. Because of the ubiquitous nature of the basic enzymatic processes in the soil, the biological processes responsible for the production of NO, N_2O and CH₄, nitrification/denitrification and methanogenesis/methanotropy are discussed in general terms. Soil water content and nutrient availability are key controls for production, consumption and emission of these gases. Intensive studies of CH₄ exchange in rice production systems made during the past decade reveal new insight. At the same time, there have been relatively few measurements of CH₄, N_2O or NO_x fluxes in upland tropical crop production systems. There are even fewer studies in which simultaneous measurements of these gases are reported. Such measurements are necessary for determining total greenhouse gas emission budgets. While intensive agricultural systems are important global sources of N₂O and CH₄ recent studies are revealing that the impact of tropical land use change on trace gas emissions is not as great as first reports suggested. It is becoming apparent that although conversion of forests to grazing lands initially induces higher N-oxide emissions than observed from the primary forest, within a few years emissions of NO and N₂O generally fall below those from the primary forest. On the other hand, CH₄ oxidation is typically greatly reduced and grazing lands may even become net sources in situations where soil compaction from cattle traffic limits gas diffusion. Establishment of tree-based systems following slash-and-burn agriculture enhances N₂O and NO emissions during and immediately following burning. These emissions soon decline to rates similar to those observed in secondary forest while CH₄ consumption rates are slightly reduced. Conversion to intensive cropping systems, on the other hand, results in significant increases in N₂O emissions, a loss of the CH₄ sink, and a substantial increase in the global warming potential compared to the forest and tree-based systems. The increasing intensification of crop production in the tropics, in which N fertilization must increase for many crops to sustain production, will most certainly increase N-oxide emissions. The increase, however, may be on the same order as that expected in temperate crop production, thus smaller than some have predicted. In addition, increased attention to management of fertilizer and water may reduce trace gas emissions and simultaneously increase fertilizer use efficiency.     

Soil management practices for sustainable agro-ecosystems

A doubling of the global food demand projected for the next 50 years poses a huge challenge for the sustainability of both food production and global and local environments. Today’s agricultural technologies may be increasing productivity to meet world food demand, but they may also be threatening agricultural ecosystems. For the global environment, agricultural systems provide both sources and sinks of greenhouse gases (GHGs), which include carbon dioxide (CO₂), methane (CH₄), and nitrous oxide (N₂O). This paper addresses the importance of soil organic carbon (SOC) for agro-ecosystems and GHG uptake and emission in agriculture, especially SOC changes associated with soil management. Soil management strategies have great potential to contribute to carbon sequestration, since the carbon sink capacity of the world’s agricultural and degraded soil is 50–66% of the historic carbon loss of 42–72 Pg (1 Pg=10¹⁵ g), although the actual carbon storage in cultivated soil may be smaller if climate changes lead to increasing mineralization. The importance of SOC in agricultural soil is, however, not controversial, as SOC helps to sustain soil fertility and conserve soil and water quality, and organic carbon compounds play a variety of roles in the nutrient, water, and biological cycles. No-tillage practices, cover crop management, and manure application are recommended to enhance SOC storage and to contribute to sustainable food production, which also improves soil quality. SOC sequestration could be increased at the expense of increasing the amount of non-CO₂ GHG emissions; however, soil testing, synchronized fertilization techniques, and optimum water control for flooding paddy fields, among other things, can reduce these emissions. Since increasing SOC may also be able to mitigate some local environmental problems, it will be necessary to have integrated soil management practices that are compatible with increasing SOM management and controlling soil residual nutrients. Cover crops would be a critical tool for sustainable soil management because they can scavenge soil residual nitrogen and their ecological functions can be utilized to establish an optimal nitrogen cycle. In addition to developing soil management strategies for sustainable agro-ecosystems, some political and social approaches will be needed, based on a common understanding that soil and agro-ecosystems are essential for a sustainable society.     

Trends in food production and nitrous oxide emissions from the agriculture sector in India: environmental implications

We studied trends in food production and nitrous oxide emissions from India's agricultural sector between 1961 and 2000. Data from Food and Agricultural Statistics (FAO) have been gathered covering production, consumption, fertilizer use and livestock details. IPCC 1996 revised guidelines were followed in studying the variations in N₂O-N emissions. Results suggest that total N₂O-N emissions (direct, animal waste and indirect sources) increased ~6.1 times from ~0.048 to ~0.294 Tg N₂O-N, over 40 years. Source-wise breakdown of emissions from 1961–2000 indicated that during 1961 most of the N₂O-N inputs were from crop residues (61%) and biological nitrogen fixation (25%), while during 2000 the main sources were synthetic fertilizer (~48%) and crop residues (19%). Direct emissions increased from ~0.031 to ~0.183 Tg. It is estimated that ~3.1% of global N₂O-N emissions comes from India. Trends in food production, primarily cereals (rice, wheat and coarse grains) and pulses, and fertilizer consumption from 1961–2000 suggest that food production (cereals and pulses) increased only 3.7 times, while nitrogenous fertilizer consumption increased ~43 times over this period, leading to extensive release of nitrogen to the atmosphere. From this study, we infer that the challenge for Indian agriculture lies not only in increasing production but also in achieving production stability while minimizing the impact to the environment, through various management and mitigation options.     

Perceptions of climate change,multiple stressors and livelihoods on marginal African coasts

Studies of multiple stressors in Africa often focus on vulnerable inland communities. Rising concentrations of the world’s poor live in coastal rural–urban areas with direct dependencies on marine as well as terrestrial ecosystem goods and services. Using participatory methods we elicited perceptions of stressors and their sources, impacts and consequences held by coastal communities in eastern Africa (Mtwara in Tanzania and Maputo in Mozambique). Respondent-informed timelines suggest wars, economic policies and natural increase have led to natural resource-dependent populations in marginal, previously little-inhabited lowland coastal areas. Respondents (n = 91) in interviews and focus groups rank climate stressors (temperature rise/erratic rain) highest amongst human/natural stressors having negative impacts on livelihoods and wellbeing (e.g., cross-scale cost of living increases including food and fuel prices). Sources of stress and impacts were mixed in time and space, complicating objective identification of causal chains. Some appeared to be specific to coastal areas. Respondents reported farms failing and rising dependence on stressed marine resources, food and fuel prices and related dependence on traders and credit shrunk by negative global market trends. Development in the guise of tourism and conservation projects limited access to land–sea livelihoods and resources in rural–urban areas (coastal squeeze). Mental modelling clarified resource user perceptions of complex linkages from local to international levels. We underline risks of the poor in marginal coastal areas facing double or multiple exposures to multiple stressors, with climate variability suggesting the risks of climate change.     

Biogeochemistry of Chinese estuarine and coastal waters: nutrients, trace metals and biomarkers

The dissolved and particulate trace metals in large and middle-sized Chinese rivers remain comparable with other less-disturbed world systems. Levels of nutrients in Chinese rivers are high due to erosion over the drainage area and the application of chemical fertilizers, which induces an N/P ratio up to 100–1,000. The concentrations of organic pollutants in Chinese rivers are ranked at the lower end of those of world systems; however, pollution has been identified in coastal waters from north to south of the country. In estuarine and coastal waters, dissolved trace metals illustrate a feature of remobilization, while non-conservative distribution is observed, with exceptions for iron and aluminum. Particulate trace metals demonstrate a fairly stable distribution along the salinity gradient, when the absolute concentration is normalized to reference materials. In high-turbidity estuaries, seaward nutrient flux can be increased by a factor of 5–10. Finally, the N/P ratio approaches 10–20 at the interior of the East China Sea, indicating that in coastal regions photosynthesis changes from P to N and Si limitations. Electronic Publication     

The Hungarian national climate change strategy: its principles, assignments, and a special case study on maize production

Efficient protection against global climate change requires international emission reduction measures. Before these ones are decided, the individual states should make arrangements within their own scope of authority for preventing and mitigating the adverse impacts of climate change already in progress as a consequence of carbon dioxide emissions done so far. In spring 2008 Hungary—among the very first ones in the international stage—passed a middle-term National Climate Change Strategy, which determines both the national tasks in order to reduce greenhouse gas emissions, and sectoral tasks of the adaptation to the ongoing climate change for the period of 2008–2025. As a concrete case study we investigated the possible impacts of the regional change in atmospheric carbon dioxide concentration, temperature and precipitation conditions of the Carpathian Basin on the cultivation conditions of maize, based on the downscaled IPCC 2007 scenarios. Temperatures of each scenarios increased significantly to basic run (1961–1990). This change suppressed the positive influence of elevated CO₂ on carbon assimilation. Serious depression may be waited during extreme hot days at Keszthely, Hungary.     

Modelling future impacts of air pollution using the multi-scale UK Integrated Assessment Model (UKIAM)

Integrated assessment modelling has evolved to support policy development in relation to air pollutants and greenhouse gases by providing integrated simulation tools able to produce quick and realistic representations of emission scenarios and their environmental impacts without the need to re-run complex atmospheric dispersion models. The UK Integrated Assessment Model (UKIAM) has been developed to investigate strategies for reducing UK emissions by bringing together information on projected UK emissions of SO₂, NO_x, NH₃, PM₁₀ and PM_2.5, atmospheric dispersion, criteria for protection of ecosystems, urban air quality and human health, and data on potential abatement measures to reduce emissions, which may subsequently be linked to associated analyses of costs and benefits. We describe the multi-scale model structure ranging from continental to roadside, UK emission sources, atmospheric dispersion of emissions, implementation of abatement measures, integration with European-scale modelling, and environmental impacts. The model generates outputs from a national perspective which are used to evaluate alternative strategies in relation to emissions, deposition patterns, air quality metrics and ecosystem critical load exceedance. We present a selection of scenarios in relation to the 2020 Business-As-Usual projections and identify potential further reductions beyond those currently being planned.     

Anthropogenic-driven changes with focus on the coastal zone of Mauritius, south-western Indian Ocean

Some 44% of the world's population lives within 150 km of the coast and mass migration towards the coast will continue in the decades ahead. Degrading and exhaustive uses of land, water and other coastal resources and disruption of environmental processes through degradation of environmental quality and loss of critical terrestrial and aquatic habitats can lead to serious deleterious impacts on the health and productivity of coastal ecosystems. Following the Arusha Resolution (1993), the Seychelles Statement (1996) and the Colombo CZM Workshop (1999), the need for integrated coastal zone management has become critical because of the limited land resources and unproportional domination of coastal areas in the wider Caribbean and Indian Ocean/ Pacific island states. The coastal zone of Mauritius (1,850 km², 20°S, 58°E, south-western Indian Ocean, 1.12 million inhabitants) was redefined in 1997 in the Environmental Protection Act of 1991 [Part VII (Act 34)] to include all islets within the Exclusive Economic Zone (EEZ; 1.7 million km²). During the 1980s, the Mauritian economy underwent major structural changes successfully, with a rapid phase of industrialization diversifying into two major activities, textiles and tourism. Existing reports and data in a common framework have to be synthesized and organized to fill existing gaps in knowledge with data collection and scientific inquiries, to identify social and economic drivers and to relate socioeconomic change to demands for environmental resources (land use, water resources, marine systems) and environmental impacts as proposed under the MERMAID (Mauritius Environmental Resource Management and Industrial Development) project. Nutrient flux and sediment trace metal contamination studies are currently underway to investigate different watersheds impacted by agricultural, urban and industrial activities in the north-west of the island. There is a pressing need to integrate the natural sciences with socioeconomic disciplines as proposed by the International Human Dimensions Program (IHDP) for an integrated management of coastal zones. Three integrated pilot projects in the Pacific-Indian Ocean and wider Caribbean as identified by Land Ocean Interaction in the Coastal Zone (LOICZ) in the future, including current status and changes in material fluxes from drainage basins, transboundary impacts from the ocean and atmospheric inputs, could elucidate the land–sea interactions and human dimensions of change on small islands. The sustainability of marine resources and the conservation of biological diversity will depend on a critical understanding of linkages between human activities and ecological responses and upon a citizenry that assumes ownership of these regions. Case studies would also help in investigating how humans affect transport pathways and biogeochemical cycles in small island states. Electronic Publication     

Global estimates of soil carbon sequestration via livestock waste: a STELLA simulation

It has become increasingly well documented that human activities are enhancing the greenhouse effect and altering the global climate. Identifying strategies to mitigate atmospheric carbon dioxide emissions on the national level are therefore critical. Fossil fuel combustion is primarily responsible for the perturbation of the global carbon cycle, although the influence of humans extends far beyond the combustion of fossil fuels. Changes in land use arising from human activities contribute substantially to atmospheric carbon dioxide; however, land use changes can act as a carbon dioxide sink as well. A soil carbon model was built using STELLA to explore how soil organic carbon sequestration (SOC) varies over a range of values for key parameters and to estimate the amount of global soil carbon sequestration from livestock waste. To obtain soil carbon sequestration estimates, model simulations occurred for 11 different livestock types and with data for eight regions around the world. The model predicted that between 1980 and 1995, United States soils were responsible for the sequestration of 444–602 Tg C from livestock waste. Model simulations further predicted that during the same period, global soil carbon sequestration from livestock waste was 2,810–4,218 Tg C. Our estimates for global SOC sequestration are modest in proportion to other terrestrial carbon sinks (i.e. forest regrowth); however, livestock waste does represent a potential for long-term soil carbon gain. SOC generated from livestock waste is another example of how human activities and land use changes are altering soil processes around the world. Readers should send their comments on this paper to: BhaskarNath@aol.com within 3 months of publication of this issue.     

全球气候变化与区域气象及空气质量的关系研究——以成都市为例

区域气象条件及空气质量或与全球气候变化关系密切。研究通过分析不同气候条件下成都地区1951～2017年主要气象要素及其2013～2017年大气污染物浓度变化趋势,并结合大数据挖掘技术探究厄尔尼诺/拉尼娜事件与成都地区气象及空气质量的关系。结果表明,全球气候变化对区域气象及空气质量影响明显。异常气候造成成都地区气温、降水、风速、日照时长等气象条件发生明显变化。这些变化通常利于大气扩散条件的改善而使污染物浓度下降,但相应时期的臭氧浓度却有所升高。研究同时利用KNN大数据挖掘算法评估不同气候条件下气象和减排对空气质量改善的贡献。结果显示,在全球厄尔尼诺发生频繁的2015年,成都地区重污染天数明显减少,气象和减排的贡献率分别为27%和73%;而在全球拉尼娜现象频发的2016年,成都地区空气质量也有明显改善,重污染天数的减少有42%归功于气象条件的变化,几乎与大气污染物的减排贡献相当。因此,为实现空气质量的有效改善,空气质量改善管理政策的制定,既要从源头上控制污染物的排放,同时也应考虑全球气候变化的影响。     

长江口潮间带湿地涨退潮期N2O的排放通量研究

随着河口区接收上游人为氮排放量的增加,为这一区域氧化亚氮（N2O）的排放增加了很大不确定性。选择长江河口潮间带湿地为研究对象,分别采用原位静态箱法和静态顶空法,从2011年1月至12月对长江口沉积物 大气界面以及涨潮水 大气界面的N2O排放通量进行了为期一年的现场观测和研究。研究结果表明,沉积物 大气界面N2O通量有着显著的时空差异。N2O排放通量在日变化以及季节变化上都表现出明显的源汇转变,就年平均排放通量,光滩带沉积物 大气界面达到了599 μgN2O/(m2〖DK〗·h),而海三棱藨草盐沼带与大气间N2O交换则十分微弱,为060 μgN2O/(m2〖DK〗·h)。对长江口涨退潮期光滩和草滩上覆水体 大气界面N2O排放通量的研究表明,长江口涨退潮期在夏季和秋季,无论是光滩还是草滩均表现为大气N2O的稳定排放源,其中夏季平均253 μgN2O/(m2〖DK〗·h),秋季平均排放通量为207 μgN2O/(m2〖DK〗·h)。作为河口区上游排放氮素的直接接收者,和沉积物 大气界面N2O排放相比,长江口涨潮水 大气界面N2O排放稳定而又显著,是长江口N2O排放的主要贡献者,应成为这一区域N2O排放的关注热点     

Tracking chemicals in products around the world: introduction of a dynamic substance flow analysis model and application to PCBs

Dynamically tracking flows and stocks of problematic chemicals in products (CiPs) in the global anthroposphere is essential to understanding their environmental fates and risks. The complex behavior of CiPs during production, use and waste disposal makes this a challenging task. Here we introduce and describe a dynamic substance flow model, named Chemicals in Products - Comprehensive Anthropospheric Fate Estimation (CiP-CAFE), which facilitates the quantification of time-variant flows and stocks of CiPs within and between seven interconnected world regions and the generation of global scale emission estimates. We applied CiP-CAFE to polychlorinated biphenyls (PCBs), first to evaluate its ability to reproduce previously reported global-scale atmospheric emission inventories and second to illustrate its potential applications and merits. CiP-CAFE quantifies the pathways of PCBs during production, use and waste disposal stages, thereby deducing the temporal evolution of in-use and waste stocks and identifying their long-term final sinks. Time-variant estimates of PCB emissions into air, water and soil can be attributed to different processes and be fed directly into a global fate and transport model. By capturing the international movement of PCBs as technical chemicals, and in products and waste, CiP-CAFE reveals that the extent of global dispersal caused by humans is larger than that occurring in the natural environment. Sensitivity analysis indicates that the model output is most sensitive to the PCB production volume and the lifetime of PCB-containing products, suggesting that a shortening of that lifetime is key to reducing future PCB emissions.     

Tackling environmental issues in industrial ceramic sintering of sewage sludge: odors and gas emissions

The inertization of sewage sludge in ceramic matrices to be used in structural or red ceramic material for buildings has proved to be a good case of reuse of waste material. However, its practical application has not yet been fully implemented in real-case scenarios, and environmental concern seems to be the main hurdle to overcome for its definitive massive approval by the building industry. In this contribution, air emissions related to the sintering of ceramic bricks made of mixtures of clay with some percentage of sewage sludge have been analyzed (in terms of gases, suspended particles and odors). Tests conducted during this work have shown higher VOC emissions in samples with some percentage of sludge in their composition (still under the regulated emission limit values), and some of them (mercaptans) are associated with odor nuisances. Besides, limit emissions values were exceeded by three inorganic pollutants (suspended particles, NO_x and HCl). Measurements in an industrial scenario test showed a high variability in air pollution emissions, suggesting the need of in situ testing for definitive implementation. With the experience collected in this and several previous works in the area of emissions related to the production of added sewage sludge ceramic, some guidelines and recommendations are given to minimize the environmental impact of ceramic production plants implementing this particular waste revalorization process. Guidelines cover different aspects: workplace implementation of gas cleaning equipment; geographical context and local wind pattern analysis; monitoring of emission and immission levels; and information policy through social control participation procedures for reporting of nuisance episodes.     

Carbon trading: time for industry involvement

Carbon trading is no longer just theory. Infant markets already exist and, in 2002, they traded perhaps $10 million worth of emissions allowances. We estimate conservatively that, by 2010, the EU scheme will trade as much as $1 billion in allowances each year. The motor of the carbon markets is a worldwide effort to reduce emissions of greenhouse gases. Its most visible symbol is the Kyoto Protocol of 1997, formally known as the United Nations Framework Convention on Climate Change. Even if Kyoto is not ratified and, despite the US's decision to opt out of the treaty, the genie of greenhouse-gas reduction is out of the bottle. We believe that trading of greenhouse gases will be a real, day-to-day activity by 2010, almost certainly in Europe and probably in Canada and Japan. Carbon trading in these areas will affect the US, whether or not America sets up a programme of its own. The conclusion of this study is that industry should get involved in defining carbon trading-and now-to advance and defend their interests. Interest should be greatest among producers and users of the greenhouse gases other than carbon dioxide, namely methane, nitrous oxide, hydrofluorocarbons, perfluorocarbons and sulphur hexafluoride.     

A new type of refrigerator and its cycle

The world is facing an energy and climate crisis. Globally, the energy sector emits 26 billion tonnes of CO₂ each year, and electricity production alone accounts for 41% of emissions (European Wind Energy Association. 2008. Pure Power: Wind Energy Scenarios up to 2030. European Wind Energy Association. p. 6). Currently, reducing CO₂ emissions and curbing climate change have become global priorities, and we only have a narrow window of time left in which to act. The new type of refrigerator can offer an immediate and concrete solution to the many energy and climate challenges that we are facing. This is an account of a new type of refrigerator and its cycle for use in the refrigeration industry. For its cycle, the working substance is air or other gases; its cycle is very similar to that of the reverse Brayton cycle (Hou, Y., Zhao, H. L., Chen, C. Z., and Xiong, L. Y. 2006. “Developments in Reverse Brayton Cycle Cryocooler in China.” Cryogenics 46 (5): 403–407). In the cycle of the new type of refrigerator, the isochoric exothermic process and the isothermal exothermic compression process replace the isobaric exothermic compression process of the reverse Brayton cycle. The new type of refrigerator can produce a net electrical energy, and it is not a perpetual motion machine, because the environmental enthalpy and atmospheric pressure can be utilized as the external energy sources, which cannot be performed by any other conventional refrigerators; therefore, the reliability and significance of this new type of refrigerator is self-evident.     

An analysis of the environmental pressure exerted by the eucalyptus-based kraft pulp industry in Thailand

The study reported here focuses on the environmental pressure exerted by large-scale eucalyptus-based kraft pulp industry in Thailand. The objective of this study was to identify the most important sources of greenhouse gases, acidifying and eutrophying compounds and tropospheric ozone precursors, human toxicity compounds and solid waste associated with the kraft pulp industry. To this end, we performed an environmental systems analysis of the kraft pulp industry system in which we distinguished between two subsystems: the eucalyptus forestry subsystem and the kraft pulp production subsystem. The results indicate that the environmental pressure is caused by the kraft pulp production subsystem rather than by the eucalyptus forestry one. The chemical recovery unit was found to be the most important source of carbon dioxide (CO₂) and sulfur dioxide (SO₂) and responsible for more than one-half of the emissions of greenhouse gases and acidifying compounds from eucalyptus-based kraft pulp production in Thailand. Biomass combustion in the energy gene ration unit is an important source of nitrogen oxide (NO _x ) and carbon monoxide (CO) which in turn are responsible for over 50% of the emissions of tropospheric ozone precursors. About 73% of the eutrophication is caused by biological aerobic wastewater treatment emitting phosphorus (P). With respect to the eucalyptus forestry, only fertilizer use in eucalyptus plantations is a relevant source of pollution through the emission of nitrous oxide (N₂O) and phosphate (PO ₄ ³⁻ ).     

Smoke-haze pollution: a review of the 1997 episode in Southeast Asia

In the second half of 1997, large areas in Southeast Asia were severely affected by a smoke-haze pollution episode caused by the emissions of an estimated 45,600 km² of vegetation that burnt on the Indonesian islands Kalimantan and Sumatra. To document the impacts of these fires on air quality, data for total suspended particulate matter (TSP) and for particulate matter below or equal to 10 microns in diameter (PM₁₀) from selected sites in Indonesia, Malaysia and Singapore are analysed in this paper. These data are supplemented by meteorological data, satellite images and a summary of related research. TSP was above 2,000 μg m^–3 for several days in Indonesian locations close to the most extensive fire activity. In Malaysia and Singapore, ambient particle concentrations increased to several times their average September levels. Characteristically for emissions from vegetation burning, the additional atmospheric particle loading during the smoke-haze episode was predominantly due to an increase of the fraction below or equal to 2.5 microns in diameter (PM_2.5). Due to the dominance of respirable particles (PM_2.5) in the smoke-haze, air quality reporting based on TSP or PM₁₀ may be inadequate to assess the health risk. Upgrading of PM_2.5 monitoring facilities is therefore needed. Reducing the probability of similar smoke-haze events in future would require appropriate fire use and smoke management strategies. Electronic Publication     

Influence of climate on the atmospheric radiocarbon concentration

In this paper, the climate effect on the atmospheric radiocarbon concentration is estimated using the data, derived by using dendrochronologically dated tree ring samples, on sunspot number and global surface temperature during 1650–1800 A.D.; however, in order to use the data as a record of changes in radiocarbon production rate or cosmic ray intensity, the variations due to the geochemical process must be eliminated. The estimated influence of climate on the atmospheric radiocarbon concentration is 3–5 times greater than the direct contribution of the change of radiocarbon concentration through a Maunder minimum. The influence of climate on the atmospheric radiocarbon concentration through a transfer rate of CO₂ between atmosphere and ocean was estimated at a rate of −13% per degree.The elimination of variations caused by climate and sunspot activities from the variations in atmospheric radiocarbon concentration gives a long time scale trend having a minimum and maximum which occur in about the seventh century A.D. and the sixth millennium suggesting a good correlation between this trend of variation and paleogeomagnetic data.     

Variations of anthropogenic CO2 in urban area deduced by radiocarbon concentration in modern tree rings

Radiocarbon concentration in the atmosphere is significantly lower in areas where man-made emissions of carbon dioxide occur. This phenomenon is known as Suess effect, and is caused by the contamination of clean air with non-radioactive carbon from fossil fuel combustion. The effect is more strongly observed in industrial and densely populated urban areas. Measurements of carbon isotope concentrations in a study area can be compared to those from areas of clear air in order to estimate the amount of carbon dioxide emission from fossil fuel combustion by using a simple mathematical model. This can be calculated using the simple mathematical model. The result of the mathematical model followed in this study suggests that the use of annual rings of trees to obtain the secular variations of ¹⁴C concentration of atmospheric CO₂ can be useful and efficient for environmental monitoring and modeling of the carbon distribution in local scale.     

Changing air quality in Delhi,India: determinants,trends, and policy implications

Air pollution is a major environmental problem in urban areas worldwide. Delhi, the capital city of India, is no exception to the universal pattern of deteriorating urban air quality with concentration of pollutants being well above the recommended WHO levels. The magnitude and urgency of the problem as a global environmental issue needs a systematic understanding of the potential causes of pollution and their contribution to air quality. In the present study, ambient air quality data (1987–2006) of SO₂, NO₂, SPM, and RSPM were analyzed to asses the changing air quality in the study area and to evaluate the effect of measures taken to control it. The primary data were collected from 1,583 households to examine the relationship between outdoor and indoor pollution level. Based on the data, the current study concludes that despite the implementation of different pollution-controlling measures, the pollutants, especially the particulate pollutants, were well above the standard limits set by CPCB. Integration between technological and social approach of urban planning is required to mitigate and manage urban environmental problems in sustainable manner.